Turbulent Drag Reduction by Biopolymers in Large Scale Pipes

In this work, we describe drag reduction experiments performed in a large diameter pipe (i.d. 100mm) using a semirigid biopolymer Xanthan Gum (XG). The objective is to build a self-consistent data base which can be used for validation purposes. To aim this, we ran a series of tests measuring friction factor at different XG concentrations (0.01, 0.05, 0.075, 0.1, and 0.2% w/w XG) and at different values of Reynolds number (from 758 to 297,000). For each concentration, we obtain also the rheological characterization of the test fluid. Our data is in excellent agreement with data collected in a different industrial scale test rig. The data is used to validate design equations available from the literature. Our data compare well with data gathered in small scale rigs and scaled up using empirically based design equations and with data collected for pipes having other than round cross section. Our data confirm the validity of a design equation inferred from direct nu- merical simulation (DNS) which was recently proposed to predict the friction factor. We show that scaling procedures based on this last equation can assist the design of piping systems in which polymer drag reduction can be exploited in a cost effective way.